package com.dzt.androidframework.widgets;

import android.content.Context;
import android.graphics.Canvas;
import android.util.AttributeSet;
import android.view.View;
import android.widget.ListAdapter;
import android.widget.ListView;

public class PinnedHeaderListView extends ListView {

	public interface PinnedHeaderAdapter {
		int PINNED_HEADER_GONE = 0;
		int PINNED_HEADER_VISIBLE = 1;
		int PINNED_HEADER_PUSHED_UP = 2;

		int getPinnedHeaderState(int position);

		void configurePinnedHeader(View header, int position, int alpha);
	}

	private static final int MAX_ALPHA = 255;
	private PinnedHeaderAdapter mAdapter;
	private View mHeaderView;
	private boolean mHeaderViewVisible;
	private int mHeaderViewWidth;
	private int mHeaderViewHeight;

	public PinnedHeaderListView(Context context) {
		super(context);
	}

	public PinnedHeaderListView(Context context, AttributeSet attrs) {
		super(context, attrs);
	}

	public PinnedHeaderListView(Context context, AttributeSet attrs,
								int defStyle) {
		super(context, attrs, defStyle);
	}

	@Override
	protected void onLayout(boolean changed, int l, int t, int r, int b) {
		super.onLayout(changed, l, t, r, b);
		if (mHeaderView != null) {
			mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
			configureHeaderView(getFirstVisiblePosition());
		}
	}

	@Override
	protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
		super.onMeasure(widthMeasureSpec, heightMeasureSpec);
		if (mHeaderView != null) {
			measureChild(mHeaderView, widthMeasureSpec, heightMeasureSpec);
			mHeaderViewWidth = mHeaderView.getMeasuredWidth();
			mHeaderViewHeight = mHeaderView.getMeasuredHeight();
		}
	}

	public void setPinnedHeaderView(View view) {
		mHeaderView = view;
		if (mHeaderView != null)
			setFadingEdgeLength(0);
		requestLayout();
	}

	public void setAdapter(ListAdapter adapter) {
		super.setAdapter(adapter);
		mAdapter = (PinnedHeaderAdapter) adapter;
	}

	public void configureHeaderView(int position) {
		if (mHeaderView == null) {
			return;
		}
		int state = mAdapter.getPinnedHeaderState(position);
		switch (state) {
			case PinnedHeaderAdapter.PINNED_HEADER_GONE:
				mHeaderViewVisible = false;
				break;
			case PinnedHeaderAdapter.PINNED_HEADER_VISIBLE:
				mAdapter.configurePinnedHeader(mHeaderView, position, MAX_ALPHA);
				if (mHeaderView.getTop() != 0) {
					mHeaderView.layout(0, 0, mHeaderViewWidth, mHeaderViewHeight);
				}
				mHeaderViewVisible = true;
				break;
			case PinnedHeaderAdapter.PINNED_HEADER_PUSHED_UP:
				View firstView = getChildAt(0);
				int bottom = firstView.getBottom();
				int headerHeight = mHeaderView.getHeight();
				int y;
				int alpha;
				if (bottom < headerHeight) {
					y = bottom - headerHeight;
					alpha = MAX_ALPHA * (headerHeight + y) / headerHeight;
				} else {
					y = 0;
					alpha = MAX_ALPHA;
				}
				mAdapter.configurePinnedHeader(mHeaderView, position, alpha);
				if (mHeaderView.getTop() != y) {
					mHeaderView.layout(0, y, mHeaderViewWidth, mHeaderViewHeight
							+ y);
				}
				mHeaderViewVisible = true;
				break;
			default:
				break;
		}
	}

	@Override
	protected void dispatchDraw(Canvas canvas) {
		super.dispatchDraw(canvas);
		if (mHeaderViewVisible) {
			drawChild(canvas, mHeaderView, getDrawingTime());
		}
	}
}
